1. Field of the Invention
The present invention relates to electrical contacts, and particularly to electrical contacts used in electrical connectors for connecting electronic packages such as pin grid array (PGA) central processing units (CPUs) with circuit substrates such as printed circuit boards (PCBs).
2. Description of the Prior Art
Zero insertion force, low actuation force connectors are widely used for electrically connecting PGA CPUs with PCBs. Usually, these connectors comprise an insulative base and a plurality of contacts received in the base. Examples of such connectors are disclosed in U.S. Pat. No. 6,319,038 and TW Patent Issue No. 472962. Referring to FIGS. 3 and 4, each contact 6 comprises a medial portion 60, a solder portion 62 depending from the medial portion 60, and a pair of arm portions 61 extending upwardly from the medial portion 60. The medial portion 60 has a U-shaped horizontal cross-section. The medial portion 60 comprises a pair of sidewalls 600 parallel to each other, and an engaging member 601 below one of the sidewalls 600. The engaging member 601 has several protrusions, for engaging with an insulative base (not shown) and thereby mounting the contact 6 in the base. The solder portion 62 extends downwardly from a bottom of the engaging member 601, for electrically connecting with a PCB (not shown). Each arm portion 61 extends upwardly from a top of a respective sidewall 600, thereby defining a first line 602 at a junction of the sidewall 600 and the arm portion 61. The arm portions 61 are bent obliquely toward each other, and are each deflectable from a rest position to a deflected position (as depicted with broken lines in FIG. 4) by a corresponding horizontally actuatable pin 8 of a CPU. Each arm portion 61 comprises a contact portion 610 at a top end thereof, and guiding portion 611 extending obliquely from an end of the contact portion 610. The contact portions 610 of the arms 61 are parallel to each other, and define a first distance therebetween. A second line 613 is defined at a bottom edge of each contact portion 610 and its adjacent guiding portion 611. The guiding portions 611 of the arms 61 extend obliquely away from each other, thereby defining a second maximum distance therebetween. The second distance is greater than the first distance.
Referring particularly to FIG. 4, in use, the pin 8 is inserted into a space between the free ends of the guiding portions 611. The second distance is greater than a diameter of the pin 8. Accordingly, the pin 8 is inserted with zero insertion force as between the contact 6 and the pin 8, and each arm portion 61 remains in the rest position. Then the pin 8 is moved horizontally toward the contact portions 610. Opposite side portions of a leading periphery of the pin 8 eventually contact insides of the guiding portions 611, whereupon an actuation force is applied to drive the pin 8 further. Finally, the pin 8 is received between the contact portions 610. During driving of the pin 8, a desired radius of leverage corresponding to the actuation force is represented by distance xe2x80x98bxe2x80x99. However, in fact, as can be seen from the broken lines of FIG. 4, when the pin 8 contacts the insides of the guiding portions 611, the arm portions 61 deflect outwardly with respect to the first lines 602 toward respective deflected positions. The pin 8 contacts a contact point of each guiding portion 611 which is located on the second line 613, and the radius of leverage corresponding to the actuation force is in fact distance xe2x80x98b primexe2x80x99 (xe2x80x98bxe2x80x99). Thus, the actuation force required to drive the pin 8 into the contact 6 is greater than desired.
In view of the above, a new electrical contact that overcomes the above-mentioned disadvantages is desired.
Accordingly, an object of the present invention is to provide an electrical contact used in an electrical connector, whereby friction between the contact and a corresponding mating pin is minimized.
Another object of the present invention is to provide an electrical contact used in an electrical connector, whereby minimal actuation force is required to drive a corresponding mating pin into engagement with the contact.
To achieve the above-mentioned objects, an electrical contact in accordance with a preferred embodiment of the present invention is used in an electrical connector. The contact is for engaging with a corresponding horizontally actuatable pin of a CPU. The contact comprises a medial portion, a pair of arm portions extending from a top of the medial portion, and a solder portion depending from a bottom of the medial portion. The medial portion comprises an engaging portion for engaging with an insulative base of the connector. The solder portion depends from a bottom of the engaging portion, for engaging with a PCB. Each arm portion is deflectable from a rest position to a deflected position by the pin. Each arm portion comprises a contact portion at a top end thereof, and a guiding portion extending obliquely from an end of the contact portion. The guiding portion comprises an inner convex side and a bottom edge. The contact portion also has an inner convex side. As each arm portion is deflected from the rest position to the deflected position, the pin contacts a contact section of the arm portion, the contact section being located above the bottom edge.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: